High temperature circuits are becoming a reality with the advent of silicon carbide substrate. Recent developments include a circuit that can withstand temperatures of up to 300.degree. C. for short periods of time. These circuits generally comprise silicon carbide transistors, resistive and capacitive elements and metallic interconnects mounted on an aluminum oxide substrate (ceramic). While ceramics can withstand high temperature, the material used to bond the discrete device to the substrate can not. Subjected to these high temperatures, the bonding material melts, breaks down, or degrades. Alternate bonding mediums can be cumbersome to use and do not have high temperature properties.
Currently, bonding silicon carbide to a substrate is conducted in a bond and etch back technique for fusing two silicon waters together, leaving a silicon dioxide layer in between. While this process produces a carbide/substrate module, these cannot hold up to the high temperature applications as our instant invention.
U.S. Pat. No. 5,098,494 to Arnold Reisman discloses a process for bonding first and second ceramic parts which may be bonded by forming bonding layers of silicon dioxide, silicon, metal or metal oxide on the parts, placing the bonding adjacent layers next to each other and heating in an oxidizing atmosphere to form an oxide bond therebetween. A layer of silicon dioxide may be formed on the first and second ceramic parts prior to bonding first and second ceramic parts. Reisman's bonding technique is used for bonding two ceramic parts at temperature lower than their melting points.
U.S. Pat. No. 4,352,120 to Kurihara et al. discloses a method of bonding silicon carbide to silicon carbide by forming silicon dioxide on at least one of the surfaces to be bonded. A conductive layer, for example copper, is then evaporated on one silicon dioxide surface and the two surfaces are solder-bonded together.